1. Field of the Invention
This invention relates to railroad car coupler systems and more particularly to draft gear assemblies for such systems where the assembly includes replaceable friction bore wear liners to interact with friction shoes of the assembly.
2. Prior Art
Coupler systems for modern railroad cars typically include a draft gear assembly to cushion and absorb forces placed on the system during car operation. Means to cushion and absorb such forces may comprise a spring package connecting with a frictional restraint device. This frictional restraint device in turn may include a set of friction shoes positioned in friction shoe seats formed in a friction bore section of a housing of the assembly. The impacting force is absorbed by friction between the shoes and friction shoe seats during shoe movement which movement also acts to compress the spring package.
Similar cushioning and absorbing means are used in other railroad component systems, for example between a bolster and a side frame of a car truck and in connection with a bolster center plate.
Some earlier frictional restraint devices had shoes which interacted with wear liners rather than directly with a housing of the device. In recent times use of such liners has been largely discontinued because of manufacturing difficulties.
One early example of a frictional restraint device and spring package used in connection with a locomotive truck center plate is disclosed in U.S. Pat. No. 2,151,603. A series of coil springs connect with a pair of friction shoes. The shoes slideably engage a pair of liners in sliding contact with an inside of a casing. During travel of the railroad locomotive, for example about a curved section of track, the trucks tend to move apart. This movement is transferred to the springs through the friction shoes and regulated accordingly.
A further railroad car shock absorbing device is set forth in U.S. Pat. No. 2,624,567. This device has a wedge which during inward movement forces a set of friction shoes apart to slide compressively over adjacent side portions of a set of wear liners positioned between the shoes. This inward shoe movement is restrained by compression of a spring and friction between the shoes and liner side portions.